The torque converter clutch is a fluid-operated friction device engageable to couple the impeller (input) and turbine (output) of a fluidic torque converter. In the usual application, the clutch is either fully released to permit unrestrained slippage between the impeller and turbine, or fully applied to prevent such slippage entirely. In some applications, the clutch may be operated in a slipping mode as well; see, for example, the Grimes U.S. Pat. No. 4,582,185, issued Apr. 15, 1986, and assigned to the assignee of the present invention.
In order to control the clutch slippage or to effect a controlled, progressive engagement of the clutch by known means, apparatus similar to that set forth in the above-referenced U.S. Pat. No. 4,582,185 would generally be required for torque capacity control. That apparatus comprises: a directional valve for directing fluid pressure to the converter for either applying or releasing the clutch, depending on its operating state; a first solenoid operated valve for controlling the operating state of the directional valve for enabling/disabling application of the clutch; and a second solenoid operated valve (such as a PWM valve) for developing the fluid pressure.